Adjustable wheel assembly

ABSTRACT

An improved wheel assembly comprises a caster fork, a caster wheel rotatably supported by the caster fork, and a caster swivel post defining an axis about which the caster fork rotates. The caster swivel post is being adapted to rotate about a pivot axis within a cylindrical housing. Alternatively, the wheel assembly has an adjustable axle for varying the camber angle of a wheel. The wheel assembly comprises a housing and an axle supported by the housing. The axle in turn rotatably supports a wheel. The axle is adapted to rotate about a pivot axis within a cylindrical housing.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional PatentApplication No. 60/386,050, filed on Jun. 5, 2002.

BACKGROUND OF INVENTION

[0002] This invention relates in general to improvements in wheelassemblies of the type used with wheelchairs and other devices. Moreparticularly, this invention relates to an improved caster wheelassembly having an adjustable caster swivel post for varying the angleof the caster swivel post to ensure that the caster swivel post remainsin a vertical orientation. Moreover, this invention relates to animproved rear wheel assembly having an adjustable axle for varying thecamber angle of the axle.

[0003] Caster wheel assemblies in general are well known in the art foruse with many different types of castered devices. Such caster wheelassemblies are commonly employed as the front wheels in a typicalwheelchair. Each caster wheel assembly typically includes a caster fork,which rotatably supports a relatively small diameter caster wheel, andwhich further includes a generally upright caster swivel post capturedby appropriate caster post bearings for rotation about a swivel axiswithin a fixed cylindrical housing. The fixed housing is adapted in turnfor mounting onto frame components of the wheelchair, or other castereddevice. Such caster wheel assemblies beneficially provide a high degreeof turning maneuverability.

[0004] The caster swivel post defines a vertically oriented axis aboutwhich the caster fork rotates. The caster post bearings are typicallyused to provide a smooth, frictionless pivot. The caster wheel isrotatably supported by the caster fork via a caster wheel axle, which issituated rearward with respect to the caster swivel post.

[0005] This ensures that the caster wheel axle is always trailing thecaster swivel post in the direction of travel. The rearward offsetdistance of the caster wheel axle with respect to the caster swivel postis commonly referred to as the “rake”. The caster swivel post must beoriented vertically to ensure that the caster wheel remains in contactwith a supporting surface as the caster fork pivots about the casterswivel post. This vertical orientation ensures that the caster wheelwill not lift off the supporting surface while turning.

[0006] Wheelchairs and other castered devices typically incorporate anumber of adjustments, including wheel height adjustment, wheel camberadjustment, and wheel size adjustment. Such adjustments are common withregard to the rear wheels of the wheelchair to allow a wheelchairoccupant to customize the wheelchair to his or her anthropometry ordriving conditions. When any of these adjustments are made, the angle ofthe caster swivel post changes and must also be adjusted to ensure thatthe caster swivel post remains vertical. Various means have been used toachieve caster swivel post angle adjustment, and are currently availableon the market. Such means are typically bulky, heavy, and cumbersome forthe user to adjust.

[0007] What is needed is an improved adjustable wheel assembly having aunique means for providing adjustability and that is a very compact,lightweight, and easy for the user to adjust.

SUMMARY OF INVENTION

[0008] The present invention is directed toward an improved caster wheelassembly that meets all the foregoing needs. The caster wheel assemblycomprises a caster fork, a caster wheel rotatably supported by thecaster fork, and a caster stem defining an axis about which the casterfork rotates. The caster stem is being adapted to rotate about a pivotaxis within a cylindrical housing.

[0009] Moreover, this invention relates to an improved wheel assemblyhaving adjustable axle for varying the camber angle of a wheel. Thewheel assembly comprises a housing and an axle supported by the housing.The axle, in turn, rotatably supports a wheel. The axle is adapted torotate about a pivot axis within a cylindrical housing.

[0010] Various objects and advantages of this invention will becomeapparent to those skilled in the art from the following detaileddescription of the preferred embodiment, when read in light of theaccompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

[0011]FIG. 1 is a front elevational view of an improved caster wheelassembly according to the invention.

[0012]FIG. 2 is a cross-sectional view of the caster wheel assemblytaken along the lines 2-2 in FIG. 1.

[0013]FIG. 3 is an exploded perspective view of the caster wheelassembly illustrated in FIGS. 1 and 2.

[0014]FIG. 4 is a reduced cross-sectional view of the caster wheelassembly illustrated in FIG. 2, wherein the caster swivel post isadjusted forward with respect to the housing.

[0015]FIG. 5 is a reduced cross-sectional view of the caster wheelassembly illustrated in FIG. 2, wherein the caster swivel post isadjusted rearward with respect to the housing.

[0016]FIG. 6 is a sectional view of an improved caster wheel assemblyaccording to another embodiment of the invention, wherein the casterswivel post is adjusted forward with respect to the housing.

[0017]FIG. 7 is a cross-sectional view of an improved caster wheelassembly according to yet another embodiment of the invention, whereinthe caster swivel post is adjusted rearward with respect to the housing.

[0018]FIG. 8 is a cross-sectional view of an improved caster wheelassembly according to still another embodiment of the invention, whereinthe caster swivel post is adjusted forward with respect to the housing.

[0019]FIG. 9 is a cross-sectional view of an improved caster wheelassembly according to another embodiment of the invention, wherein thecaster swivel post is adjusted forward with respect to the housing.

[0020]FIG. 10 is a partial sectional view of an improved rear wheelassembly according to the invention, wherein the axle sleeve isadjustable to change the camber angle of the rear wheel.

DETAILED DESCRIPTION

[0021] Referring now to the drawings, there is illustrated in FIGS. 1-3an improved caster wheel assembly 10 for use with many different typesof castered devices (not shown). Caster wheel assemblies 10 according tothe invention are particularly useful as the front wheels in a typicalwheelchair (not shown). The caster wheel assembly 10 comprises a casterfork 12, which rotatably supports a relatively small diameter casterwheel 14, and which further includes a generally upright caster swivelpost 16 captured by the caster fork 12 by appropriate caster postbearings 18. The caster swivel post 16 is adapted to pivot about a pivotaxis A1 within a fixed cylindrical housing 20. The fixed housing 20 isadapted, in turn, for mounting onto frame components of the wheelchairor other castered device. The caster wheel assembly 10 provides a highdegree of turning maneuverability.

[0022] The caster swivel post 16 defines a vertically oriented axisabout which the caster fork 12 rotates. This axis is coincident with thepivot axis A1 described about.

[0023] The caster post bearings 18 are typically used to provide asmooth, frictionless pivot.

[0024] The caster wheel 14 is rotatably supported by the caster fork 12via a caster wheel axle 22, which is situated rearward, or toward theright when viewing FIG. 2, with respect to the caster swivel post 16.This ensures that the caster wheel axle 22 is always trailing the casterswivel post 16 in the direction of travel, or toward the left whenviewing FIG. 2. The caster swivel post 16 must be oriented vertically,or along the vertically oriented axis A1, to ensure that the casterwheel 14 remains in contact with a supporting surface (not shown) as thecaster fork 12 pivots about the caster swivel post 16. This verticalorientation ensures that the caster wheel 14 will not lift off thesupporting surface while turning.

[0025] Continuing with reference to FIGS. 2-3, the caster post bearings18 are preferably press fit within the caster fork 12 so that the casterpost bearings 18 are concentric with respect to one another. Althoughtwo caster post bearings 18 are shown, it should be appreciated by oneof ordinary skill in the art of the invention that one or more casterpost bearings or bushings may be suitable for carrying out theinvention. An internal retaining ring 24 is provided for retainingand/or spacing the caster post bearings 18 within the housing 20. A flatwasher 26 is provided within the internal retaining ring 24 andconcentric with the caster post bearings 18. The flat washer 26 isprovided to maintain a spaced relation between the inner raceway 18 a ofthe caster post bearings 18.

[0026] The caster swivel post 16 is comprised of a stem bolt 28 having ashaft 28 a having a lower end that mates with the inner raceway 18 a ofthe caster post bearings 18. This allows the stem bolt 28 to rotatefreely with respect to the caster fork 12. An upper end of the shaft 28a of the stem bolt 28 is threaded so as to thread into a pivot nut 30within the housing 20. A pivot pin 32 passes through a cross-hole 30 ain the pivot nut 30, such that the pivot nut 30 can rotate about thepivot pin 32, or about a pivot axis A2 defined by the pivot pin 32,while remaining captive within the housing 20. The pivot pin 32 is heldfixed within the housing 20. The pivot pin 32 may be comprised of, butis not limited to, a bolt and nut, a dowel pin with one or moreretaining rings, or a pin, such as the pivot pin 32 shown, with acentral tapped hole 32 a held secure by two end screws 32 b.

[0027] A spline assembly, generally indicated at 34, resides between thehousing 20 and an upper one of the caster post bearings 18 within thecaster fork 12. The spline assembly 34 comprises an upper spline 36 thatis in fixed relation to the housing 20 and a lower spline 38 that is ina fixed relation to the caster fork 12. The upper and lower splines 36,38 can be integral with the corresponding housing 20 and caster fork 12or may be supported on separate members, as illustrated in the drawings.The upper spline 36 has a central slot 36 a therein while the lowerspline 38 has a central hole 38 a. The stem bolt 28 passes through thecentral hole 38 a in the lower spline 38 and the central slot 36 a inthe upper spline 36. When the stem bolt 28 is tightened into the pivotnut 30, teeth 38 b on the lower spline 38 lock into engagement with themating teeth 36 b on the upper spline 36, fixing the angular position ofthe caster swivel post 16 with respect to the frame of the wheelchair orcastered device (not shown). The center of curvature of the spline teeth36 b, 38 b is coincident with the pivot axis A2. The teeth 38 b, 36 b onthe lower and upper splines 38, 36 are preferably spaced two degreesapart along this radius of curvature, providing two-degree increments ofadjustment of the caster swivel post 16 with respect to the frame of thewheelchair or castered device. Because the pivot nut 30 can rotate aboutthe pivot axis A2, the pivot nut 30 remains aligned with the stem bolt28 over the range of angle adjustment of the caster swivel post 16. Thetotal range of adjustment of the caster swivel post 16 is limited by theclearance between the inner diameter 20 a of the housing 20 and theouter diameter 30 c of the pivot nut 30. According to a preferredembodiment of the invention, the inside diameter 20 a of the housing 20and outside diameter 30 b of the pivot post 30 are dimensioned to permita total adjustment range of about eight degrees forward and rearwardrelative to the housing 20, as shown in FIGS. 4 and 5. It should beappreciated by one of ordinary skill in the art of the invention thatthe caster wheel assembly 10 could be modified to provide coarser orfiner increments of adjustment, or a different range of adjustment,depending on the particular wheelchair or castered device application.

[0028] In operation, the stem bolt 28 can be loosened until the teeth 36b on the upper spline 36 and the teeth 38 b on the lower spline 38separate enough to clear one another. The pivot nut 30 is then pivotedabout the pivot axis A2 until the new desired angle is achieved. Asclearly illustrated in the drawings, the pivot nut 30 can be pivotedforward relative to the housing 20, or in a counter-clockwise directionwhen viewing FIG. 4, or rearward relative to the housing 20, or in aclockwise direction when viewing FIG. 5. Ideally the angle is adjustedwith the stem bolt 28 as close to vertical when the wheelchair or othercastered device (not shown) is on a level supporting surface. The stembolt 28 is then tightened, causing the spline teeth 36 b, 38 b toengage, locking the caster swivel post 16 in a desired angular position.

[0029] The foregoing caster wheel assembly 10 is very compact andlightweight. This is achieved by placing the caster post bearings 18 inthe caster fork 12, rather than in the housing 12. Placing the casterpost bearings 18 in this location allows the pivot assembly to occupythe housing 12. Because most of the angle adjustment components areinternal to either the housing 20 or the caster fork 12, the design isextremely compact and efficiently integrated into the wheelchair orother castered device. This produces a lightweight and low profileappearance.

[0030] It should be clearly understood that the present invention is notintended to be limited in scope to the preferred embodiment of theinvention described hereinabove.

[0031] Several examples of alternative embodiments of the invention aredescribed hereinbelow.

[0032] As illustrated in FIG. 6, an upper end 40 a of a pivot stem bolt40, instead of the pivot nut 30 illustrated above, can be supportedwithin the housing 20 by the pivot pin 32. A stem nut 42 beneath of thecaster post bearings 18 on the lower end 40 b of the pivot stem bolt 40serves to fix the spline assembly 34 between the caster post bearings 18and the housing 20 so as to retain the caster swivel post in a desiredangular position. The form and function of this embodiment is similar tothe embodiment described above.

[0033] Another embodiment of the invention is illustrated in FIG. 7.This embodiment of the invention comprises an angled wedge 44 betweenthe caster post bearings 18 and the housing 20. The wedge 44 functionsto retain the caster swivel post 16 in a desired angular position. Thewedge 44 is secured in compression between the caster post bearings 18and an engagement key slot 46 a in a slotted member 46 fixed relative tothe housing 20. In order to adjust the angle of the caster swivel post16, the wedge 44 is removed from the assembly, and reoriented, orreplaced by a wedge, or series of wedges, having a different angle.Mating features on the engagement key slot 46 a and the wedge 44 ensurethat the wedge 44 is properly aligned when installed. These featuresallow the wedge 44 to be installed in two different positions byrotating the wedge 180 degrees about the caster swivel post 16. Itshould be appreciated by one of ordinary skill in the art of theinvention that the invention is not intended to be limited to the wedgeshown but may be carried out with any components with mating orinterlocking shapes, including but not limited to components havingcurved surfaces, hexentric shapes, curved acme threads, and curvedunified threads.

[0034] Yet another embodiment of the invention is illustrated in FIG. 8.This embodiment of the invention comprises a pivot nut 48 that resideswithin a housing 50, and which is allowed to rotate about a pivot axisA2 within the housing 50. Two setscrews 52 are threaded into the pivotnut 48 and bear against the housing 20 above and below the pivot axis A2to prevent the pivot nut 48 from pivoting. The setscrews 52 are used toadjust and fix the angle of the pivot nut 48 with respect to thewheelchair or other castered device (not shown). The user can change theangle of the pivot nut 48 by adjusting setscrews 52 accordingly to fixthe angle of the pivot nut 48 with respect to the wheelchair or othercastered device. For example, to change the angle of the pivot nut 48 sothat the pivot nut 48 pivots rearward, or in a counterclockwisedirection when viewing FIG. 8, the user loosens the upper setscrew 52,or moves the upper setscrew 52 to the left when viewing FIG. 8, andtightens the lower setscrew 52, or moves the lower setscrew 52 to theright when viewing FIG. 8. The upper setscrew 52 resist movement of thepivot nut 48 in a counter-clockwise direction when viewing FIG. 8 andthe lower setscrew 52 resist movement of the pivot nut 48 in a clockwisedirection when viewing FIG. 8. It should be appreciated by one ofordinary skill in the art of the invention that the threaded setscrews52 may be threaded into a pivot stem bolt instead of the pivot nut 48shown.

[0035] Still another embodiment of the invention is illustrated in FIG.9. This embodiment of the invention comprises a spline assembly 54similar in function to the spline assembly 34 of the preferredembodiment set forth above, except that the pivot axis has been omitted.A spline insert 56 fixed within the housing 58 has upper and a lowerspline surfaces 56 a, 56 b. These spline surfaces 56 a, 56 b are curved,having curvature that is concentric with a virtual axis A3 about whichthe pivot stem bolt 60 rotates when assuming different angularpositions. The pivot stem bolt 60 has a concave spline surface 60 a thatengages the upper spline insert surface 56 a. A spline washer 62 has anupper spline surface 62 a that engages the lower spline insert surface56 b. A stem nut 64 tightened beneath the caster post bearings 18secures the angular position of the pivot stem bolt 60.

[0036] It further should be appreciated that the present invention isnot intended to be limited in scope to caster assemblies, as set forthabove, but could be applied to the rear wheels of a wheelchair (notshown) to allow for camber adjustment of the rear wheels. For example,there is illustrated in FIG. 10 a rear wheel assembly 66 comprising ahousing 68, such as the cylindrical camber tube shown, that is adaptedto be supported by the frame of a wheelchair (not shown). An axle sleeve70 is supported by to the camber tube 68. An axle 72 is in turn adaptedto be inserted into the axle sleeve 70 to rotatably support a relativelylarge diameter rear wheel 74 relative to the axle sleeve 70. The axle 72may include one or more spring balls 72 a that function to capture theaxle 72 in the axle sleeve 70. The rear wheel 74 provides a drivingforce for propelling the wheelchair.

[0037] The axle 72 defines an axis A4 about which the rear wheel 74rotates. Wheel bearings 76 are used to permit the axle 72 to rotatesmoothly and without significant friction. The wheel bearings 76 arepreferably press fit within the hub 74 a of the rear wheel 74 so thatthe wheel bearings 76 are concentric with respect to one another. Aninner end of the axle sleeve 70 is threaded so as to thread into a pivotnut 78 within the camber tube 68. A pivot pin 80 passes through across-hole 78 a in the pivot nut 78, such that the pivot nut 78 canrotate about the pivot pin 80, or about a pivot axis A5 defined by thepivot pin 80, while remaining captive within the camber tube 68. Thepivot pin 80 is held fixed within the camber tube 68.

[0038] A spline assembly, generally indicated at 82, resides between thecamber tube 68 and an axle sleeve nut 84 on an outer end of the axlesleeve 70. The spline assembly 82 comprises an inner spline 86, which isin fixed relation to the camber tube 68, and an outer spline 88. Theinner spline 86 has a central slot 86 a therein while the outer spline88 has a central hole 88 a. The axle sleeve 70 passes through thecentral hole 88 a in the outer spline 88 and the central slot 86 a inthe inner spline 86. When the axle sleeve nut 84 is tightened into theaxle sleeve 70, teeth 88 b on the outer spline 88 lock into engagementwith the mating teeth 86 b on the inner spline 86, fixing the angularposition of the axle sleeve 70 with respect to the frame of thewheelchair (not shown).

[0039] It should be clearly understood that the invention is notintended to be limited in scope to the rear wheel assembly describedhereinabove and that the invention can be practiced in numerousalternative embodiments including, for example, embodiments similar tothose set forth above and illustrated in FIGS. 6-9.

[0040] The principle and mode of operation of this invention have beenexplained and illustrated in its preferred embodiment. However, it mustbe understood that this invention may be practiced otherwise than asspecifically explained and illustrated without departing from its spiritor scope.

What is claimed is:
 1. A caster wheel assembly comprising: a casterfork; a caster wheel rotatably supported by the caster fork; a casterswivel post defining an axis about which the caster fork rotates, thecaster swivel post being adapted to rotate about a pivot axis within acylindrical housing.
 2. The caster wheel assembly according to claim 1further comprising an upper spline that is in fixed relation to thehousing and a lower spline that is in a fixed relation to the casterfork, the lower spline being adapted to lock into engagement with theupper spline to fix the angular position of the caster swivel post withrespect to the housing.
 3. The caster wheel assembly according to claim1 further comprising an angled wedge between the caster fork and thehousing to retain the caster swivel post in a desired angular position.4. The caster wheel assembly according to claim 1 further comprisingsetscrews that are threaded into the caster swivel post and bear againstthe housing to prevent the caster swivel post from pivoting.
 5. Thecaster wheel assembly according to claim 1 wherein the caster swivelpost rotates about an axis perpendicular to the caster swivel post. 6.The caster wheel assembly according to claim 1 further comprising matingsurfaces that lock together under the tension in order to fix the angleof the caster swivel post with respect to the housing.
 7. A wheelassembly comprising: a housing; an axle supported by to the housing andwhich in turn rotatably supports a wheel, the axle being adapted torotate about a pivot axis within a cylindrical housing.
 8. The wheelassembly according to claim 7 further comprising an inner spline that isin fixed relation to the housing and an outer lower spline that isadapted to lock into engagement with the inner spline to fix the angularposition of the axle with respect to the housing.
 9. The wheel assemblyaccording to claim 7 further comprising an angled wedge between thewheel and the housing to retain the axle in a desired angular position.10. The wheel assembly according to claim 7 further comprising setscrewsthat are threaded into the axle and bear against the housing to preventthe axle from pivoting.
 11. The wheel assembly according to claim 7wherein the axle rotates about an axis perpendicular to the axle. 12.The wheel assembly according to claim 7 further comprising matingsurfaces that lock together under the tension in order to fix the angleof the axle with respect to the housing.